COMPARISON OF MILKCLOTTING CHARACTERISTICS OF CRUDE KIWIFRUIT (Actinidia deliciosa) AND GINGER (Zingiber officinale) PROTEASES IN SOFT CHEESEMAKING

Abstract

The main objective of this dissertation work was to perform comparative study on the milkclotting characteristics of crude kiwifruit (Actinidia deliciosa) and ginger (Zingiber officinale) proteases in soft cheesemaking. The effect of crude kiwifruit and ginger protease on physicochemical and microbial characteristics of soft cheese prepared were examined. Temperature and pH of the milk on milk clotting activity (MCA) and time of coagulation (TOC) were optimized by response surface methodology (RSM). The protease activity and protein concentration of the crude kiwifruit and ginger protease were also measured in optimized conditions. Finally, the cheese prepared by using crude kiwifruit and ginger protease were compared with rennet cheese for physicochemical and microbial properties. Numerical optimization study revealed that optimum condition of milk clotting for kiwifruit and ginger were found to be 61°C (at pH 6.5) and 55°C (at pH 5.5) respectively. The optimized TOC and MCA for crude kiwifruit protease were found to be 120.513 s and 492.630 units respectively. Similarly, TOC and MCA for crude ginger protease were 1591.667 s and 241.988 units respectively. The physico-chemical analysis showed that there was non-significant difference (P>0.05) in protein content among cheeses made using rennet and crude plant proteases while significant difference (P<0.05) was observed in moisture, fat, ash, calcium, acidity, pH and cheese yield. Microbiological analysis showed the absence of coliform in all three cheeses. Similarly, significant difference (P<0.05) was observed in the total plate count (TPC) of all three samples while non-significant difference (P>0.05) was found in the count of yeast and mold